In ink jet recording, small ink drops are released by a variety of different mechanisms so as to form a dot image on printing paper. Unlike the case of dot impact printing, this method is not noisy, makes it easy to obtain full color images, and permits printing to be performed at high speeds.
However, as the ink used in ink jet recording is usually a water-based ink based on a direct dye or acidic dye, it has poor drying properties.
The properties required of the paper used in ink jet recording are as follows:
(1) Permits fast ink drying, PA0 (2) Permits high printing speeds, PA0 (3) Gives little spreading, tailing or blurring of dots.
Conventionally, property (1) was improved by providing an ink jet recording layer comprising a silica of large specific surface area so as to increase ink absorption. However, if the ink absorption is increased too much, the print density falls. A method was therefore developed to control the amount of voids in recording paper in order to solve this problem, as is described in Japanese Tokko Sho 63-22997.
Due to recent progress in ink jet printers and more diverse needs, a requirement has emerged for better resolution and higher image quality. However, using an ink jet recording paper having a recording layer with a pigment of large specific surface area, the recording layer surface has low smoothness. As a result, the appearance of the image was lacking in quality, the dots were not perfect circles, and the reproducibility of the image was unsatisfactory.
To improve the smoothness of the recording layer surface, conventional pigment-coated ink jet recording papers were given a supercalendar treatment or other treatment. This improved gloss and smoothness, but the porous structure of the ink jet recording layer was destroyed. Consequently, ink absorption amount and ink absorption speed declined, and drying properties were poorer.
There are also resin-coated ink jet recording papers which have a relatively smooth surface. However, as this type of paper contains almost no pigments of large specific surface area, ink absorption amount and absorption speed were low.
In ink jet recording, aqueous ink where a dye is dissolved in water are used, but if the water adheres to the paper, the image tends to blur and run after printing. In the case of resin-coated papers, water-soluble resins are generally used, so this tendency was particularly acute.
After carrying out many studies on ink jet recording papers to solve the aforesaid problems, the Inventors found it was possible to obtain a recording surface of high gloss and smoothness, obtain a large ink absorption amount and high ink absorption speed, and confer water resistance on the image. These discoveries led to the present invention.